Inert environment enclosure

ABSTRACT

A novel inert environment enclosure includes an object inlet where production objects enter the enclosure and an object outlet where the production objects exit. At least one of the object inlet and the object outlet includes both a top-side flow obstructer and a bottom-side flow obstructer for preventing air from entering the enclosure. In a particular embodiment, the top-side flow obstructer and the bottom-side flow obstructer each include a curtain constructed from a flexible fabric having a plurality of individual adjacent fingers. In another particular embodiment, the inert environment enclosure is a nitrogen hood that houses a wave soldering machine. A inert gas nozzle is mounted at or near the inlet and/or the outlet. The inert environment enclosure maintains a positive pressure with respect to the surrounding environment when production objects are passed through the enclosure.

RELATED APPLICATIONS

This application claims the benefit of copending U.S. Provisional PatentApplication No. 61/271,722, filed Jul. 24, 2009 by the same inventors,which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to manufacturing equipment, and moreparticularly to inert environment enclosures. Even more particularly,the invention relates to a feature for improving the performance ofinert environment enclosures.

2. Description of the Background Art

In the electronics manufacturing industry, large-scale solderingprocesses and devices are currently being used to solder electricalcomponents onto production objects such as, for example, printed circuitboards (PCB's). Typically, PCB's include multiple plated through-holes(PTHs), which receive the leads of electrical components that are to besoldered. Electrical components are typically mounted on the top surfaceof the PCB such that the leads pass through the PTHs and are exposedfrom the bottom surface of the PCB.

One process, commonly known in the art as “wave soldering”, enablesseveral electrical joints to be soldered in a short period of time. Wavesoldering typically involves passing multiple production boards througha wave soldering machine by way of a conveyor system. Production boardsare either loaded directly onto the conveyor system, or multipleproduction boards are arranged onto a pallet that is loaded onto theconveyor system. As production boards move along the conveyor, theyundergo a sequence of processes. For example, after entering themachine, the production board passes over a fluxer which applies a layerof flux onto it's bottom surface. Then, the production board passes overa heater where it is preheated to prevent thermal shock caused by suddenexposure to molten solder. After being preheated, the entire bottomsurface of the production board passes over a wave of molten solder,which is projected upward via a solder nozzle. The molten soldercontacts the entire bottom surface, then foams joints on any areas notcovered by soldermask. The solder nozzle is supplied by a solderreservoir, which also catches any of the molten solder that does notstick. Any solder that returns to the reservoir mixes with the othermolten solder and is eventually re-projected from the nozzle.

Although conventional wave soldering machines can solder several jointsrelatively quickly, there are drawbacks. For example, oxygen in the airreacts with the solder to form oxides (e.g., tin-oxide, lead-oxide,etc.) which accumulate on the solder nozzle and other machinecomponents. The oxides block solder flow and, therefore, must be removedto achieve acceptable soldering. Of course, the removal of the oxidesrequires preventative maintenance (PM) and, therefore, equipment andmanufacturing downtime. In addition, oxide formation consumes valuablesolder that must be continuously replaced with new solder. As yetanother drawback, oxides create environmentally hazardous materials(i.e. lead oxide).

In effort to decrease the problems caused by oxide formation, equipmentmanufacturers have designed wave soldering machines that operate withininert environment enclosures such as, for example, nitrogen hoods. Anitrogen hood is basically a large nitrogen filled enclosure constructedaround a machine to prevent air from contacting its components. Atypical nitrogen hood includes an inlet for receiving unsolderedproduction boards, and an outlet where finished products exit.

Although conventional nitrogen hoods help reduce the amount of oxygenwithin a workspace, problems still exist. For example, air can enterinto conventional hoods through both the inlet and the outlet.

In an effort to decrease the problems associated with conventionalnitrogen hoods, equipment manufacturers have designed nitrogen hoodswith inlet and outlet curtains. Such curtains are mounted over the inletand outlet openings to reduce air flow through the openings while alsoallowing production boards to move therethrough. When production boardsare not being moved into or out of such hoods, the curtains hangdownward to prevent air from entering. As conveyors guide productionboards through the inlet or outlet, the curtains brush the top surfaceof the production boards to form a light “seal” between the top of theopening and the top of the production object.

Although such curtains help prevent air from entering when productionboards are not being moved into or out of the hood, air still enters thehood when the machine is in use. As production objects pass into, or outof, the hood, the curtains are lifted thereby permitting the flow of airunder the bottom-side of the production object.

What is needed, therefore, is an inert environment enclosure thatreduces the amount of air and/or any other potentially unwanted gasesthat enter the enclosure when production objects are passedtherethrough.

SUMMARY

The present invention overcomes the problems associated with the priorart by providing an inert environment enclosure that includes featuresfor reducing the amount of gas that can enter the enclosure from thelocal surrounding environment.

According to an example embodiment of the present invention, an inertenvironment enclosure includes a wall defining an interior and anexterior of the enclosure, at least one gas inlet that is coupled toprovide gas to the interior of the enclosure, an object inlet throughwhich production objects enter the enclosure, and an object outletthrough which production objects exit the enclosure. At least one of theobject inlet and the object outlet includes a top-side flow obstructerand a bottom-side flow obstructer for inhibiting gases from the exteriorof the enclosure from entering the interior of the enclosure. Thetop-side flow obstructer is adapted to contact top surfaces of theproduction objects and the bottom-side flow obstructer is adapted tocontact the opposite bottom surfaces of the production objects.

In an example embodiment, the gas inlet is positioned at one of theobject inlet and the object outlet. The enclosure further includes aflow controller for controlling the flow of gas through the gas inlet.The flow of gas through the gas inlet is controlled so as to maintain apositive pressure in the interior of the enclosure with respect to theexterior of the enclosure. In a particular embodiment, the flowcontroller provides a substantially continuous flow of gas through thegas inlet to maintain the positive pressure, even when productionobjects are being passed through the enclosure. In a disclosedembodiment, the gas inlet is positioned at the object outlet. A flowmeter allows a user to control the flow of gas through the gas inlet andinto the object outlet. In an alternative embodiment, the gas inlet ispositioned at the object inlet and a second gas inlet is positioned atthe object outlet. Optionally, the gas inlet is a gas nozzle coupled toan inert gas (e.g., nitrogen) source and is operative to discharge theinert gas into the enclosure.

In a disclosed embodiment, the enclosure includes a guide system forguiding production objects into the enclosure through the object inletand out of the enclosure through the object outlet. In a specificembodiment, the guide system includes a set of tracks disposed throughthe object inlet and the object outlet. The production objects arecarried through the enclosure on pallets which are operative to carrymultiple production objects (e.g., PCB's) at once. In one exampleembodiment, the guide system is a conveyor system.

In a disclosed embodiment, at least one of the top-side flow obstructerand the bottom-side flow obstructer includes a flexible material adaptedto slidably contact passing production objects. In an exampleembodiment, the flexible material is composed of a fabric. In an evenmore particular embodiment, the fabric includes fluorocarbon and canwithstand temperatures exceeding 300 degrees Fahrenheit. In another moreparticular embodiment, the fabric is a part of the bottom-side flowobstructer. The fabric is flexible enough to be deflected downward whenurged by passing production objects, yet possesses sufficient elasticityto return to an upright position after the production objects pass. Inone embodiment, the flexible material is arranged in at least one rowtransverse to a travel direction of the production objects. Optionally,the flexible material is arranged in a plurality of rows transverse tothe travel direction of the production objects. The flexible materialincludes a first separation defining at least a first finger and anadjacent second finger. The first finger deflects independently from thesecond adjacent finger. Each row includes a first layer and an abuttingsecond layer of the flexible material.

In an example embodiment, at least one of the top-side flow obstructerand the bottom-side flow obstructer includes a first plate for mountingthe flexible material. The flexible material includes a mounting portionand a free portion. The mounting portion is fixably mounted with respectto the first plate. The free portion is adapted to slidably contactpassing production objects. The first plate includes a first surface, anopposite second surface, and an opening passing through both the firstsurface and the second surface. The flexible material is positionedthrough the opening such that the first surface of the plate faces thefree portion of the flexible material and the second surface of theplate faces the mounting portion of the flexible material. In a moreparticular embodiment, the flow obstructer also includes a second platethat has a first surface and an opposite second surface. The secondplate is fixed to the first plate such that the second surface of thefirst plate faces the first surface of the second plate. Further, themounting portion of the flexible material is sandwiched between thesecond surface of the first plate and the first surface of the secondplate.

In a disclosed embodiment, the top-side flow obstructer includes a freeportion adapted to slidably contact the top surfaces of productionobjects passing between the top-side flow obstructer and the bottom-sideflow obstructer. Likewise, the bottom-side flow obstructer includes afree surface adapted to slidably contact the bottom surfaces of theproduction objects passing between the top-side flow obstructer and thebottom-side flow obstructer. The free portion of the top side flowobstructer and the free portion of the bottom side flow obstructer areadapted to contact one another when production objects are not beingpassed between the top-side flow obstructer and the bottom-side flowobstructer.

In a more particular embodiment, the object inlet includes a top-sideflow obstructer and a bottom-side flow obstructer, and the object outletincludes a top-side flow obstructer and a bottom-side flow obstructer.The bottom-side flow obstructer of the object inlet includes a freeportion adapted to slidably contact the bottom surfaces of productionobjects passing between the bottom-side flow obstructer and the firsttop-side flow obstructer of the first object inlet. Likewise, thetop-side flow obstructer of the object inlet includes a free portionadapted to slidably contact top surfaces of the production objectspassing between the bottom-side flow obstructer and the first top-sideflow obstructer of the object inlet. The free portion of the top-sideflow obstructer and the free portion of the bottom-side flow obstructerof the object inlet are adapted to contact one another when productionobjects are not being passed between the bottom-side flow obstructer andthe top-side flow obstructer of the object inlet.

Similarly, the bottom-side flow obstructer of the object outlet includesa free portion adapted to slidably contact the bottom surfaces of theproduction objects passing between the bottom-side flow obstructer andthe top-side flow obstructer of the object outlet. The top-side flowobstructer of the object outlet includes a free portion adapted toslidably contact the top surfaces of production objects passing betweenthe bottom-side flow obstructer and the top-side flow obstructer of theobject outlet. The free portion of the top-side flow obstructer of theobject outlet and the free portion of the bottom side flow obstructer ofthe object outlet are adapted to contact one another when productionobjects are not being passed between the bottom-side flow obstructer andthe top-side flow obstructer of the object outlet.

In an example embodiment, the inert environment enclosure is a nitrogenhood. In a more particular embodiment, the nitrogen hood is adapted toreceive wave soldering equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the followingdrawings, wherein like reference numbers denote substantially similarelements:

FIG. 1 shows a perspective view of a nitrogen hood 100;

FIG. 2 shows a perspective view of an inlet 102 of nitrogen hood 100shown in FIG. 1;

FIG. 3 shows a perspective view of a bottom-side flow obstructer 202 anda top-side flow obstructer 204 of inlet 102;

FIG. 4 shows an exploded view of bottom-side flow obstructer 202 andtop-side flow obstructer 204;

FIG. 5 depicts the construction of bottom-side flow obstructer 202;

FIG. 6 shows a cross-sectioned view of inlet 102;

FIG. 7 shows a perspective view of an outlet 104 of nitrogen hood 100;

FIG. 8 shows a perspective view of a bottom-side flow obstructer 702 anda top-side flow obstructer 704 of outlet 104;

FIG. 9 shows an exploded view of top-side flow obstructer 704 and nozzle712; and

FIG. 10 shows a cross-sectioned view of outlet 104.

DETAILED DESCRIPTION

The present invention overcomes the problems associated with the priorart, by providing an inert environment enclosure having a bottom-sideflow obstructer and a top-side flow obstructer mounted over an inletand/or an outlet of the enclosure. In the following description,numerous specific details are set forth (e.g., conveyor system, nitrogenhood, wave soldering equipment, etc.) in order to provide a thoroughunderstanding of the invention. Those skilled in the art will recognize,however, that the invention may be practiced apart from these specificdetails. In other instances, details of well known wave solderingpractices (e.g., preheating, fluxing, soldering, etc.) and componentshave been omitted, so as not to unnecessarily obscure the presentinvention. Although the present invention is described in the context ofa wave soldering hood, it should be understood that the invention can beimplemented with any known processes that ordinarily take place in ahood.

FIG. 1 shows a perspective view of a wave soldering nitrogen hood 100according to one embodiment of the present invention. Hood 100 includesan inlet 102, an outlet 104, a set of conveyor tracks 106, and a controlpanel 108. Inlet 102 and outlet 104 provide passageways through whichproduction objects (e.g., circuit boards) enter and exit, respectively,hood 100. Tracks 106 provide a means for guiding production objectsthrough hood 100. Tracks 106 extend through inlet 102, passed processequipment (i.e., flux sprayers, heaters, solder wave generating device),and through outlet 104. Production objects can be transported alongtracks 106 either manually or automatically by any suitable means suchas, for example, motorized chains, belts, rollers, gears, etc. Further,the production objects can be carried along tracks 106 either directly,or on a pallet. Control panel 108 provides user control and monitoringof various functions and operating conditions of hood 100. Indeed,control panel 108 includes a set of flow meters 110 and a userinput/output interface 112. Flow meters 110 facilitate the control andmonitoring of nitrogen levels at various locations within hood 100.Further, at least one of flow meters 110 facilitates the control andmonitoring of nitrogen in outlet 104. The nitrogen gas used by hood 100during production can be supplied by any suitable source such as, forexample, refillable/removable onboard nitrogen tanks, nitrogen hosesconnected to a remote nitrogen source, etc. User input/output interface112 represents any suitable device or devices that facilitatecommunication between a user and hood 100. For example, interface 112includes a display screen 114 for providing information such asoperating conditions (e.g., internal oxygen levels, internal pressurelevels, temperature, etc.), user settings, etc. Interface 112 alsoincludes a plurality of user-input devices 116 which represent anysuitable means (e.g., buttons, switches, knobs, ect.) for receivinguser-inputs.

One important feature of hood 100 is that it can operate at a positivegage pressure during production. That is, when operating at positivegage pressure, the pressure inside hood 100 is greater than the pressureoutside of hood 100. Of course, the gage pressure is increased byincreasing the flow of nitrogen gas into hood 100. By operating at apositive gage pressure, the amount of air that can enter hood 100 issubstantially reduced because nitrogen gas continuously flows from thehigh pressure interior of hood 100 to the surrounding low pressureatmosphere. Thus, the pressure difference causes nitrogen gas to flowcontinuously out of hood 100 through any small openings that couldotherwise permit atmospheric air to pass therethrough. Not only can hood100 operate at a positive gage pressure, hood 100 can also maintain apositive gage pressure either automatically or manually. As a means formaintaining a positive gage pressure, hood 100 could employ an automaticcontrol system that maintains a predetermined set of operatingcondition. For example, the control system could include a computersystem electrically coupled to an electronic pressure indicator and anelectrically actuated nitrogen valve. The computer system couldcontinuously sample electrical pressure readings indicative of thepressure within hood, and then compare the readings to a predeterminedset of values that could be either user defined or preprogrammed. Inresponse to a reading that does not satisfy a predetermined condition,the computer system could actuate the nitrogen valve until sufficientgage pressure is achieved. That is, nitrogen flow could be increased ordecreased when gage pressure readings become too high or low,respectively. Optionally, the automatic control system could alsoinclude various other types of sensors (e.g., thermometers, lightsensors, electrical charge sensors, oxygen sensors, nitrogen sensors,etc.) and process devices (e.g., vent actuators, exhaust pumps/fans,heating/cooling elements, light sources, etc.) coupled to the computerto facilitate the automatic control and monitoring of various otheroperating conditions within hood 100. As another means for maintaining apositive gage pressure, pressure within hood 100 could be controlledmanually by simply incorporating a valve that, when actuated, maintainsa continuous flow rate of nitrogen into hood 100. The valve could beeither a variable flow rate valve, or a simple open/close type valve. Itis known to those skilled in the art that the term “gage pressure”refers to the pressure in a system relative to the local atmosphericpressure when the system pressure is greater than the local atmosphericpressure. Conversely, the term “vacuum pressure” refers to the pressurein a system relative to the local atmospheric pressure when the systempressure is less than the local atmospheric pressure.

FIG. 2 shows a perspective view of inlet 102 including additionalfeatures not visible in FIG. 1. Inlet 102 includes an opening 200 (shownin FIG. 6), a bottom-side flow obstructer 202, and a top-side flowobstructer 204. Opening 200 is formed through a sidewall 206 of hood 100and provides a passageway through which production objects are guidedinto hood 100 along tracks 106. Bottom-side flow obstructer 202 ismounted to the bottom of tracks 106 via a set of screws 208. Likewise,top-side flow obstructer 204 is mounted on the top of tracks 106 via aset of screws 210. Bottom-side flow obstructer 202 and top-side flowobstructer 204 are mounted facing one another from opposite sides oftracks 106 such that bottom-side flow obstructer 202 and top-side flowobstructer 204 simultaneously contact the top and bottom surfaces,respectively, of the production objects as they enter the hood. Thiscontact prevents air from entering hood 100 as the production objectsare passed through opening 200. During times when production objects arenot being passed through opening 200, bottom-side flow obstructer 202and top-side flow obstructer 204 contact one another to prevent air fromentering into hood 100. In addition to preventing air from entering hood100, bottom-side flow obstructer 202 and top-side flow obstructer 204reduce the flow of nitrogen out of hood 100. By reducing the flow ofnitrogen out of hood 100, less nitrogen is required to increase ormaintain gage pressures. As previously mentioned, an increase in gagepressure further prevents the passage of air into hood 100 because gasflows from the high pressure within hood 100 to the relative lowpressure of the local atmosphere outside of hood 100.

FIG. 3 shows a perspective view of bottom-side flow obstructer 202 andtop-side flow obstructer 204 including additional features not visiblein FIGS. 1-2. Bottom-side flow obstructer 202 includes a set of curtains300, a mounting plate 302, and a cover plate 304. Curtains 300 aremounted on plate 302 in an upright position such that the top ofcurtains 300 slidably contact the bottom surfaces of passing productionobjects. Curtains 300 are composed of soft flexible fabric that iseasily deflected when urged by passing production objects. In additionto being soft and flexible, the fabric has enough rigidity to maintain alight contact with the bottom surfaces of passing production objects andto allow curtains 300 to return to back to an upright position afterbeing deflected. Although curtains 300 could be constructed from varioustypes of fabrics and materials (e.g., bristles), the inventors havefound that good results are achieved when the curtains are constructedfrom a polytetrafluoroethylene (i.e. Teflon) coated fabric that iselectrostatic discharge (ESD) safe and resistant to temperaturesexceeding 300 F. Curtains 300 are arranged in four parallel rows306(a-d) extending along the entire width of opening 200 (shown in FIG.6). Each of rows 306(a-d) include a first layer 308 and an overlappingsecond layer 310, each of which include a plurality of vertical slices312 defining a plurality of adjacent fingers 314. Slices 312 formed onfirst layer 308 are horizontally offset from slices 312 formed on secondlayer 310 so as to minimize air leakage between fingers 314.

Each of fingers 314 is free to deflect independently from neighboringfingers such that curtains 300 can adapt to the various sizes andelement configurations of different production objects. As productionobjects pass through inlet 102, fingers 314 deflect downward and gentlysweep the bottom surfaces of the objects to form a light sealtherebetween.

Mounting plate 302 is, for example, an aluminum plate that facilitatesthe mounting of curtains 300. The mounting of curtains 300 is furtherfacilitated by cover plate 304 which is mounted to the bottom surface ofmounting plate 302 via a set of screws 316 (visible in FIG. 4). Notethat additional features and functionalities of mounting plate 302 andcover plate 304 will be described in further detail in view of upcomingFIG. 4.

Top-side flow obstructer 204 includes a set of curtains 318, a mountingplate 320, and a cover plate 322. Curtains 318 are mounted on plate 320in a downward position facing curtains 300 such that the bottoms ofcurtains 318 slidably contact the top surfaces of passing productionobjects. Further, curtains 318 are arranged into four rows 324(a-d) thatcontact rows 306(a-d), respectively, when objects are not being passedinto hood 100. Mounting plate 320 and cover plate 322 facilitate themounting of curtains 318. Also, plates 320 and 322 are fixed togethervia a set of screws 326. The features and functionalities of curtains318, plate 320, and plate 322 are substantially similar to the featuresand functionalities of curtains 300, plate 302, and plate 304,respectively. Therefore, in-depth details of curtains 318, plate 320,and plate 322 are omitted from the following description to avoidredundancy.

FIG. 4 shows a perspective view of bottom-side flow obstructer 202 andtop-side flow obstructer 204 exploded along an axis 400 to showadditional features of curtains 300, mounting plate 302, cover plate304, curtains 318, mounting plate 320, and cover plate 322. Curtains 300further include a mounting portion 402 that facilitates the mounting ofcurtains 300 to plate 302. Plate 302 includes a set of through-holes404, a set of threaded screw holes 406 (not visible), and four parallelslots 408. Through-holes 404 are openings formed completely throughplate 302, each of which receives a respective one of screws 208 duringthe mounting of bottom-side flow obstructer 202 to the bottom of tracks106. Each of screw holes 406 receives a respective one of screws 316during the mounting of cover plate 304 to mounting plate 302. Each ofslots 408 is an elongated opening formed completely through plate 302and is adapted to receive a respective one of rows 306(a-d). Cover plate304 includes a set of through holes 410 and a second set ofthrough-holes 412. Each of through-holes 410 is coaxially aligned with arespective one of through-holes 404 so as to receive a respective one ofscrews 208 during the mounting of bottom-side flow obstructer 202 to thebottom of tracks 106. Each of through-holes 412 is coaxially alignedwith a respective one of screw holes 406 to receive a respective one ofscrews 316 during the mounting of cover plate 304 to mounting plate 302.

Curtains 318 further include a mounting portion 414 that facilitates themounting of curtains 318 to plate 320. Plate 320 includes a set ofthrough-holes 416, a set of threaded screw holes 418, and four parallelslots 420. Through-holes 416 are openings formed completely throughplate 320, each of which receives a respective one of screws 210 duringthe mounting of top-side flow obstructer 204 to the top of tracks 106.Each of screw holes 418 receives a respective one of screws 326 duringthe mounting of cover plate 322 to mounting plate 320. Each of slots 420is an elongated opening formed completely through plate 320 and isadapted to receive a respective one of rows 324(a-d). Cover plate 322includes a set of through-holes 422 and a second set of through-holes424. Each of through-holes 422 is coaxially aligned with a respectiveone of through-holes 416 so as to receive a respective one of screws 210during the mounting of top-side flow obstructer 204 to the top of tracks106. Each of through-holes 424 is coaxially aligned with a respectiveone of screw holes 418 to receive a respective one of screws 326 duringthe mounting of cover plate 322 to mounting plate 320.

FIG. 5 depicts several stages for assembling bottom-side flow obstructer202 according to one embodiment of the present invention. The assemblystages are summarized into a first stage 500, a second stage 502, athird stage 504, and a fourth stage 506. In first stage 500, a singleuniform sheet of fabric 508, mounting plate 302, cover plate 304, andscrews 316 are provided. Then, in second stage 502, fabric 508 is weavedinto and out of each of slots 408 so as to form loops 510 of fabricextending along each respective slot 408. At this point of assembly itshould be recognized that each of loops 510 forms an individual one ofrows 306(a-d). Next, in third stage 504, cover plate 304 is tightlymounted to plate 302 via screws 316 such the mounting portion 502 istightly sandwiched and, therefore, fixed between plates 304 and 302.Once screws 316 tightened, each loop 510 is sliced vertically alonglines 512 so as to form a plurality of individual adjacent loops 514.Finally, in fourth stage 506, the crest of each individual loop 514 issliced horizontally such that each loop 514 is separated into twoindividual abutting fingers 314, one of which is part of first layer 308while the other is part of second layer 310.

FIG. 6 shows a cross-sectional view of inlet 102 when production objectsare not being passed into hood 100. Accordingly, when no productionobjects are being passed into hood 100 curtains 300 remain in an uprightposition while curtains 318 remain in a downward position such that rows306(a-d) remain in contact with rows 324(a-d), respectively. Althoughcontinuous contact is maintained between each of rows 306(a-d) andrespective rows 324(a-d) simultaneously, contact between only one out ofthe four sets of respective rows would be sufficient to prevent air fromentering hood 100. Thus, in order for air to enter through opening 200,failure to make contact at each of rows 306(a-d) and respective rows324(a-d) would have to occur simultaneously. Even if such an unlikelysituation occurred, the positive gage pressure within hood 100 wouldcause a continuous discharge of nitrogen gas out of opening 200 toprevent the air from entering into hood 100.

Not only do curtains 300 and 318 prevent air from entering opening 200when objects are not being passed into hood 100, but also when objectsare being passed into hood 100. For example, when a production objectfirst enters inlet 102, it pushes row 306(a) and row 324(a) inward andaway from one another while rows 306(b-d) and 324(b-d), respectively,remain in contact. As rows 306(a) and 324(a) are forced to deflectinward, rows 306(a) and 324(a) simultaneously contact the bottom and topsurfaces, respectively, of the production object as it passes. Any airthat might leak through rows 306(a) and 324(a) is prevented fromentering any further by the remaining contacting rows 306(b-d) and324(b-d). Likewise, rows 306(b-d) and 324(b-d) sequentially deflectinward and form a light seal with the bottom and top surfaces,respectively, of the production object as it moves forward. It is likelythat horizontal length of passing production objects will be greaterthan the horizontal length of inlet 102 such that all of rows 306(a-d)and 324(a-d) will be simultaneously deflected at the same time. However,air flow is still prevented from entering through opening 200 because ofthe positive gage pressure within hood 100 and the horizontal distancebetween the curtain rows. The distance between each row reduces air flowinto hood 100 because as fingers of one row are deflected by a part ofthe production object, fingers of another row, previously deflected bythe part, will likely be returning to a position that inhibits air flow.

FIG. 7 shows a perspective view of outlet 104 including additionalfeatures not visible in FIG. 1. Outlet 104 includes an opening 700(shown in FIG. 11), a bottom-side flow obstructer 702, and a top-sideflow obstructer 704. Opening 700 is formed through a sidewall 706 ofhood 100 and provides a passageway through which production objects areguided out of hood 100 along tracks 106. Bottom-side flow obstructer 702is mounted to the bottom of tracks 106 via a set of screws 708.Likewise, top-side flow obstructer 704 is mounted on the top of tracks106 via a set of bolts 710. Bottom-side flow obstructer 702 and top-sideflow obstructer 704 are mounted facing one another from opposite sidesof tracks 106 such that bottom-side flow obstructer 702 and top-sideflow obstructer 704 simultaneously contact the top and bottom surfaces,respectively, of the production objects as they exit hood 100. Thiscontact prevents air from entering hood 100 as the production objectsexit through outlet 104. If no production objects are exiting hood 100,bottom-side flow obstructer 702 and top-side flow obstructer 704 contactone another to prevent air from entering into hood 100. In addition topreventing air from entering hood 100, bottom-side flow obstructer 702and top-side flow obstructer 704 reduce the flow of nitrogen out of hood100.

In this particular embodiment, hood 100 further includes a nitrogennozzle 712 mounted on top-side flow obstructer 704. Nitrogen nozzle 712provides a means for feeding nitrogen gas directly into outlet 104 tofurther prevent air from entering hood 100. Nitrogen gas is fed tonozzle 712 via a nitrogen feed line 714 which is shown passing throughwall 706. Although feed line 714 is shown passing through wall 706, itcould carry nitrogen from any suitable nitrogen source regardless if thesource is positioned inside or outside hood 100. The control andmonitoring of nitrogen flow through nozzle 712 is facilitated by atleast one of flow meters 110 (shown in FIG. 1). It should be noted thatnozzle 712 generically represents any suitable means for providing acontrolled discharge of gas. However, the inventors have achieved goodresults using a Chand Eisenmann Metallurgical porous sintered, 316stainless steel nozzle.

FIG. 8 shows a perspective view of bottom-side flow obstructer 702 andtop-side flow obstructer 704 including additional features not visiblein FIG. 7.

Bottom-side flow obstructer 702 includes a set of curtains 800, amounting plate 802, and a cover plate 804. Curtains 800 are arranged infour parallel rows 806(a-d), each of which include a plurality ofadjacent fingers 808. As production objects exit outlet 104, fingers 808deflect downward and gently sweep the bottom surfaces of the objects toform a light seal therebetween. Mounting plate 802 and cover plate 804facilitate the mounting of curtains 800 and are mounted together via aset of screws 810 (shown in FIG. 10). It should be noted that thefeatures of bottom-side flow obstructer 702 are substantially similar tothose of bottom-side flow obstructer 202 and top-side flow obstructer204. Therefore, many specific details associated with the features ofbottom-side flow obstructer 702 are omitted from the followingdescription to avoid redundancy.

Top-side flow obstructer 704 includes a set of curtains 812, a mountingplate 814, and a cover plate 816. Curtains 812 are mounted on plate 814in a downward position facing curtains 800 such that the bottoms ofcurtains 812 slidably contact the top surfaces of passing productionobjects. Further, curtains 812 are arranged into three rows 818(b-d)that contact rows 806(b-d), respectively, when objects are not exitinghood 100. Each of rows 818(b-d) include a plurality of adjacent fingers820 (shown in FIG. 9). Mounting plate 814 and cover plate 816 facilitatethe mounting of curtains 812. The mounting of curtains 812 is furtherfacilitated by a set of screws 822 which provide a means for fasteningplates 814 and 816 together while portions of curtains 812 aresandwiched therebetween.

FIG. 9 shows a perspective view of curtains 812, mounting plate 814,cover plate 816, and nozzle 712 exploded along an axis 900.

Curtains 812 further include a mounting portion 902 which getssandwiched tightly between plates 814 and 816 during mounting. In thisparticular embodiment, curtains 812 are constructed from the same typeof fabric used to construct curtains 300, 318, and 800. However, thematerial used to construct one curtain need not necessarily be the sameas the material used to form another curtain. For example, curtains 812could be formed from material that is more flexible than that used toform curtains 800 because, unlike curtains 800, curtains 812 do notdeflect downward and, therefore, do not have to overcome gravity whenreturning to their original position.

Plate 814 includes a set of through-holes 904, a set of threaded screwholes 906, and three parallel slots 908. Through-holes 904 are openingsformed completely through plate 814 to receive a respective one of bolts710 during the mounting of top-side flow obstructer 704 to the top oftracks 106. Each of screw holes 906 receives a respective one of screws822 during the mounting of cover plate 816 to mounting plate 814. Eachof slots 908 is an elongated opening formed completely through plate 814and is adapted to receive a respective one of rows 818(b-d).

Cover plate 816 includes a set of through-holes 910 and a second set ofthrough-holes 912. Each of through-holes 910 is coaxially aligned with arespective one of through-holes 904 so as to receive a respective one ofbolts 710 during the mounting of top-side flow obstructer 704 to the topof tracks 106. Each of through-holes 912 is coaxially aligned with arespective one of screw holes 906 to receive a respective one of screws822 during the mounting of cover plate 816 to mounting plate 814.

Plates 814 and 816 further include through-holes 914 and 916,respectively, to facilitate the mounting of nozzle 712. Through-holes914 and 916 are coaxially aligned with respect to axis 900 so as to forman opening through top-side flow obstructer 704 when plates 814 and 816are fastened to one another. Once nozzle 712 is positioned within theopening, it is mounted in a fixed position via a nut 918 that threadsonto a complementary set of threads 920 formed on nozzle 712. Althoughnot shown, it is likely that some suitable type of gas flow obstructer(e.g., o-rings, gaskets, etc.) would also be used when mounting nozzle712.

FIG. 10 shows a cross-sectional view of outlet 104 when productionobjects are not exiting hood 100. Accordingly, when no productionobjects are exiting hood 100, curtains 800 remain in an upright positionwhile curtains 812 remain in a downward position such that rows 806(b-d)remain in contact with rows 818(b-d), respectively. In this particularembodiment, the functionalities of curtains 800 and 812 aresubstantially similar to that of curtains 300 and 318, the onlydifference being that curtains 812 have three rows rather than four.Instead of having a fourth row, nozzle 712 is mounted above row 806(a).

The description of particular embodiments of the present invention isnow complete. Many of the described features may be substituted, alteredor omitted without departing from the scope of the invention. Forexample, alternate flow-obstructing elements (e.g., bristles), may besubstituted for any of curtains 300, 318, 800, and 812. As anotherexample, alternate inerting gas (e.g., helium, argon, etc.), may besubstituted for the nitrogen gas. These and other deviations from theparticular embodiments shown will be apparent to those skilled in theart, particularly in view of the foregoing disclosure.

1. An inert environment enclosure comprising: a wall defining aninterior of said enclosure and an exterior of said enclosure; at leastone gas inlet coupled to provide gas to said interior of said enclosure;an object inlet through which production objects enter said enclosure;an object outlet through which said production objects exit saidenclosure; and wherein at least one of said object inlet and said objectoutlet includes a top-side flow obstructer and a bottom-side flowobstructer for inhibiting gases from the exterior of said enclosure fromentering said interior of said enclosure, said top-side flow obstructerbeing adapted to contact top surfaces of said production objects, saidbottom-side flow obstructer being adapted to contact bottom surfaces ofsaid production objects. 2-38. (canceled)